Coordinated Broadcast-based Request-Reply and Group Management for Tightly-Coupled Wireless Systems

TL;DR

This paper introduces a broadcast-based protocol for tightly-coupled wireless systems that improves performance and predictability of request-reply interactions, especially near channel capacity, with group management features.

Contribution

The paper presents a novel coordinated broadcast protocol that reduces message transmissions and enhances predictability in wireless distributed applications.

Findings

Significantly better performance than point-to-point methods

Maintains predictability near wireless channel capacity

Supports controlled group management operations

Abstract

As the domain of cyber-physical systems continues to grow, an increasing number of tightly-coupled distributed applications will be implemented on top of wireless networking technologies. Some of these applications, including collaborative robotic teams, work in a coordinated fashion, whereby a distinguished node takes control decisions and sends commands to other nodes, which in turn perform the requested action/operation and send back a reply/acknowledgment. The implementation of such interactions via reliable point-to-point flows may lead to a significant performance degradation due to collisions, especially when the system operates close to the capacity of the communication channel. We propose a coordinated protocol which exploits the broadcast nature of the wireless medium in order to support this application-level interaction with a minimal number of message transmissions and predictable latency. The protocol also comes with group management functionality, allowing new processes to join and existing processes to leave the group in a controlled way. We evaluate a prototype implementation over WiFi, using a simulated setup as well as a physical testbed. Our results show that the proposed protocol can achieve significantly better performance compared to point-to- point approaches, and remains fully predictable and dependable even when operating close to the wireless channel capacity.